However, that number is a one-percent decrease from the quarter that ended in June, according to Kindsight Security Labs, of Mountain View, California, in its third-quarter malware report [PDF].

Based on information gathered from service providers, Kindsight reported that 6.5 percent of the home network infections were high-level threats that could turn a home computer into a spam-spewing zombie on a botnet or compromise a computer owner's bank account.

ZeroAccess botnet

Some 2.2 million home networks worldwide are infected with malware controlled by the ZeroAccess botnet, the report estimated. In North America, one in every 125 home networks are infected with malicious software.

"The ZeroAccess.net has grown significantly to become the most active botnet we've measured this year," Kevin McNamee, Kindsight security architect and director, said in a statement.

"Cyber criminals are primarily using it to take over victim computers and conduct click fraud," McNamee continued. "With ZeroAccess, they can mimic the human behavior of clicking online ads, resulting in millions of dollars of fraud."

Kindsight estimates that online advertisers lose $900,000 a day in fraud perpetrated by ZeroAccess.

The cyber-security vendor also reported that it saw a 165% increase in the number of Android malware samples during the period. Nevertheless, despite the growth in spyware apps and malware, there have been no major malware outbreaks, the report said.

"Aggressive Adware," some of it bordering on spyware, continues to be a problem in the Android market, according to Kindsight. It estimates that three percent of all mobile devices host some form of that software.

While security software aimed at removing aggressive adware from mobile devices has been introduced into the market, the report explained, it remains to be seen how effective it will be in mitigating the problem.

Similar efforts were made in the past to address spyware problems in the Windows world, but the Android environment is a horse of a different color. "One key difference between these ad-funded Android apps and the traditional Window's variety is that the Android variety is being distributed from the Google Play App Store, which lends them considerable legitimacy," the report said.

This story, "Malware infects 13 percent of North American home networks" was originally published by
PCWorld.